The present invention relates to an improvement of a flat tube for a heat exchanger, such as in evaporator of an air conditioner for automobiles.
A conventional tube 2 of this type is, as shown in FIG. 1 comprised, of a perimetrical wall 6 and a plurality of transversally spaced inner walls 7 extending between corresponding sites on the interior of opposite broad faces of the perimetrical wall 6. In order to reduce the weight of the tube 2 and improve its performance by reducing the pressure loss in the tube, it is necessary to thin the walls 6 and 7, increasing the cross-sectional areas of the passages formed therein. It is relatively easy to thin the inner walls 7 since these need only to need the standards for pressure resistance. Therefore the thinning of inner walls has been encouraged in the past. However as to the perimetrical wall 6 it was difficult to thin the same, since in addition to meeting pressure requirements, the outer wall must possess a certain level of thickness so as to be adequately resistive for a predetermined period of time against corrosion., i.e. to the formation of pinholes made through the tube by corrosion. Corrosion of the type above explained occurs with particular intensity in regions where the environment includes high humidity and salty air.